1. Field of the Invention
The invention relates to a redundant automation system for controlling a technical apparatus, comprising a first automation device and a second automation device, where the first automation device has a first control program and the second automation device has a second control program for controlling the technical apparatus, where the first and the second control programs are each configured to execute the same control tasks for the technical process, where the first automation device has a first data interface that is connected to a field bus, and the second automation device has a second data interface that is connected to the field bus, and where a first address is assigned to the first data interface and a second address is assigned to the second data interface.
2. Description of the Related Art
A redundant automation system is also referred to as a high-availability system ((HA) system). One such HA system is a fail-safe automation system, usually comprising two linked automation devices, in particular programmable logic controllers, which jointly control a technical apparatus. Here, one automation device takes the lead at all times when controlling the technical apparatus. The leading automation device in each case is also referred to as the main automation device or master. The other automation device in each case is ready to assume responsibility for the control of the technical apparatus at any time. The other automation device is also referred to as the substitute automation device or reserve. If one of the two automation devices fails, then the entire technical process can be controlled by a single automation device, this being referred to as high availability. In a HA system, each automation device has a dedicated interface, e.g., an Ethernet interface, with a dedicated IP address for communication on a field bus.
An automation installation usually includes many subscribers, who must connect to the redundant automation system to deliver or collect process data, or to display or process the data. A large number of the aforementioned subscribers have no knowledge of the existence of a redundant automation system (2-CPU system).
Conventional HA systems have the disadvantage that the remote IP address of the HA system is not clear to subscribers who have to establish a connection to an HA system. It either has a first address for the first automation device or a second address for the second automation device. If one of the two addresses is used, and precisely that automation device having the chosen address fails, the subscriber is no longer able to establish the connection even though the HA system as a whole is still available.
This problem was previously solved by the existence of functionally enhanced subscribers (clients, HMIs) in which a further IP address is configured. If the connection to the first address fails and cannot be re-established, a second IP address is used to continue working. The disadvantage of this solution is that a special implementation for the address management is required in the subscribers.